9.1088 towlower

POSIX specification:
http://www.opengroup.org/onlinepubs/9699919799/functions/towlower.html

Gnulib module: wctype-h

Portability problems fixed by Gnulib:

• This function is missing on some platforms: IRIX 5.3, Solaris 2.5.1.
• This function returns values of which the upper 16 bits are incorrect on some platforms: mingw.
• This function cannot be called from plain inline or extern inline functions on some platforms: OS X 10.8.

Portability problems not fixed by Gnulib:

• On AIX and Windows platforms, wchar_t is a 16-bit type and therefore cannot accommodate all Unicode characters.